From the Italian utility model TO2011U000044 is known a trap provided with a tank containing a liquid, a bait and a horizontal platform, which is arranged above the tank and is formed by two trapdoors. Said trapdoors can tilt about respective horizontal axes due to the weight of a mouse, when the latter gets onto the platform while searching for the bait. In this way, the mouse slides on the tilted trapdoors and falls into the tank below, where it dies by drowning.
The trapdoors, after the catch of the mouse, return to their original horizontal position, respectively because of a counterweight and a spring. In this way, a relatively large number of mice can be caught before having to empty and refill the tank again.
In the case of rats, the traps of the above described kind are not always able to catch the animal, because the latter can sometimes recognize when the first trapdoor starts to tilt, and then identifies the danger. Therefore, the rat turns back to the trap entry without falling into the tank below and can release pheromones indicative of said danger, so that further possible catches are compromised.
Furthermore, in the case of animals of large dimensions, it is appropriate to manufacture a relatively long trapdoor, having regard to the normal size of the animal able to unbalance the trapdoor, but in this way the trap becomes very cumbersome.
On the other hand, in the case of small sized mice, their weight is sometimes not sufficient to tilt the trapdoors, for example because of friction due to moisture, rust, dirt that may accumulate between the trapdoors and the fixed structure of the trap. In these cases, the mice can eat the bait without being caught, so that the trap should be checked periodically to verify if the bait must be reintegrated inside the trap, and therefore unwanted costs and maintenance time are caused.